When building websites, we use a lot of smoke-and-mirrors to get things accomplished, and we often do it by re-purposing preexisting functionality and code. Once the page is themed, who will be the wiser, right? Unfortunately, a seemingly straightforward idea can become unwieldy when you are unfamiliar with the underlying APIs involved. Such was the case for me when I needed to be able to programmatically move a file from one file field to another in Drupal 7.
